When you attain the rank of Tleilaxu Master, you are given a special dagger that is a cross between a blade and a syringe. It can be used to drain blood from your opponents in combat and can be upgraded as you advance in tech levels.
Instructions in it's use can be found on the dagger itself.
If you ever lose your dagger, you can <reclaim> at the main guild room. Enjoy.
Requires: You must be a Tleilaxu Master